Simplify duplicate importmap handling

[dzbarsky]

What does this PR do? Why is it needed? Starlark cleanup and perf improvement - saves around 250ms on buildbuddy

• It's more efficient to ignore a duplicate archive inside the action vs in analysis phase
• I belive _transitive_archives_without_test_archives is no longer needed due to the recompile_external_deps machinery for tests
• This allows to remove some data from the providers as well

Which issues(s) does this PR fix?

Fixes #

Other notes for review

[dzbarsky]

This one needs more work